Do cleaner fish learn to feed against their preference in a reverse reward contingency task?

Area of Science:

• Cognitive Ecology
• Animal Behavior
• Neuroscience

Background:

• Impulse control is often tested using a reverse reward contingency task, where animals must choose a smaller item to gain a larger reward.
• Mammals, particularly primates, often find this task difficult, leading to the hypothesis that it is generally cognitively demanding.
• An ecological approach suggests task difficulty is linked to species-specific selective pressures on foraging behavior, not general cognition.

Purpose of the Study:

• To test the hypothesis that ecological pressures, rather than general cognitive ability, influence performance on the reverse reward contingency task.
• To investigate the impulse control capabilities of the cleaner wrasse (Labroides dimidiatus), a fish species with relevant natural foraging behaviors.

Main Methods:

• Eight cleaner wrasse individuals were tested on a reverse reward contingency task.
• Subjects had to choose a smaller food item to receive a larger one.
• A subsequent test involved a large or none contingency, followed by re-exposure to the original task.

Main Results:

• None of the tested cleaner wrasse learned the reverse reward contingency task after 200 trials.
• One individual learned a simpler large or none contingency task.
• After re-exposure, this individual then learned the reverse reward task within 30 trials.

Conclusions:

• Cleaner wrasse's natural interactions with client fish did not prepare them for the reverse reward test.
• The ability to solve reverse reward tasks may not be limited to mammals.
• This capacity could be present in species like the cleaner wrasse, where choosing non-preferred food is an ecological challenge.